South African ozone peaks with fires and winter fires
Continental South African surface ozone peaks in late winter–spring from household combustion and biomass burning, and is often VOC-limited.
Source
Seasonal influences on surface ozone variability in continental South Africa and implications for air quality
What they did
Authors analyzed continuous in situ ozone at Botsalano, Marikana, Welgegund, and Elandsfontein, related it to NOx and CO, used air-mass origin, and computed ozone production regime from a 2-year VOC dataset at Welgegund.
What they found
Sites regularly exceed the South African ozone standard. Concentrations peak in late winter and early spring: winter trapping of household-combustion pollution plus a spring biomass-burning CO source. Stratospheric intrusions are minor. Ozone correlates with CO more than NOx, and at least 40% of Welgegund production is VOC-limited amid high regional NOx.
The limits
What it doesn't show
VOC-limited inference is strongest at Welgegund; the other sites lack the same VOC record. The paper is observational, not a full photochemical-model source apportionment, and socio-economic household burning is hard to regulate from this evidence alone.
Key terms
- VOC-limited
- Ozone production increases with VOCs; cutting NOx alone may not reduce (or may raise) ozone.
- Photo-stationary state
- NOx–O3 null cycle with no net ozone until peroxy radicals make new NO2.
- Highveld
- Industrial interior plateau of South Africa with a satellite NO2 hotspot.
- Biomass burning
- Open fires in southern Africa, peaking June–September, exporting CO and ozone precursors.
- Household combustion
- Residential burning for heat that elevates winter low-level pollution.
Flashcards
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Continental South African ozone peaks in:
Common questions
When is ozone highest?
Late winter and early spring, not midsummer photochemistry alone.
Is stratospheric ozone the main surface source?
No; a very small contribution at these four sites.
Why does CO matter?
CO can drive ozone formation and tracks burning and household combustion.
NOx- or VOC-limited?
Large parts of the interior appear VOC-limited because of high anthropogenic NOx.
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